1. Field of the Invention
The present invention relates to a control device for an electric compressor in a vehicle-mounted air conditioner.
2. Description of the Related Art
In an electric vehicle-mounted air conditioner mounted on a hybrid vehicle, a fuel cell electric vehicle (FCEV), and a hydrogen vehicle, so-called sensorless control is generally used as control for an electric compressor. In the sensorless control for the permanent-magnet synchronous motor, synchronized operation cannot be performed immediately because a rotor position is unknown at the time of starting of the motor. With such reason, a three-phase voltage (current) for rotating the rotor in one direction at a constant speed is provided for a certain time to the motor to forcibly start the motor (for example, Japanese Patent Application Laid-Open No. 2003-28073). A control device for performing the sensorless control is required to be separately provided for the electric compressor.
The control device may be integrated with a housing of the electric compressor to save a mounting space. When an engine or a large motor for driving a vehicle is provided near the control device, even when the control device is integrated with the housing, it is necessary to protect the control device from heat generated by the engine or the large motor. It is also necessary to protect an internal circuit of the control device from electromagnetic waves coming from the outside and electromagnetic waves from a power electronics component and a switching circuit of the control device itself. To protect the internal circuit, for example, devices or substrates are disposed via a metallic plate or an aluminum block that is also used for fixing the devices or the substrates to a cooling device (for example, Japanese Patent Application Laid-Open No. 2004-190525).
However, such housing of the electric compressor integrated with the control device does not have a sufficient size for a size of a control substrate. In addition, there is a strong demand for a further reduction in size of the electric compressor because the electric compressor is mounted on a vehicle. Therefore, a circuit board constituting the control device is divided into two pieces to be stacked to reduce an area for housing the circuit board. However, a switching device for handling a large current is indispensable for the smooth control of the motor. As the size of the control device decreases, circuit malfunction due to noise mainly caused by the switching device in the housing occurs, and an influence of heat generated from the device on other devices causes problems.
Moreover, in a control performed by such control device, the compressor connected to the rotor does not operate stably and causes a noise. In the electric compressor as a product, noise should be eliminated as much as possible. In particular, the hybrid vehicle, the FCEV, and the hydrogen vehicle are extremely quiet because wheels of the vehicles are driven by a motor without using an engine. Therefore, the noise is likely to degrade values of the vehicles as products. If the electric compressor is controlled without grasping a position of the rotor, the likelihood of failure in starting the motor increases. In the hybrid vehicle, the FCEV, and the hydrogen vehicle, a power source is common for wheel driving and the electric compressor. Therefore, power consumption due to the failure in starting the motor should be avoided as much as possible.
It is an object of the present invention to at least solve the problems in the conventional technology.
A control device according to one aspect of the present invention is used in an electric compressor and includes a shot-pulse control unit configured to provide, at a time of starting a permanent-magnet synchronous motor, a predetermined current to each of phases of a stator of the permanent-magnet synchronous motor for such a short time that a rotor does not rotate; a detecting unit configured to detect a value indicative of a current flowing through each of the phases when the predetermined current is provided to each of the phases; and a estimating unit configured to estimate a position of the rotor by comparing values detected by the detecting unit.
A control device according to another aspect of the present invention is used in an electric compressor and includes a voltage control unit configured to control application of a voltage to a permanent-magnet synchronous motor included in or connected to the electric compressor by applying and stop applying the voltage when the electric compressor is stopped during starting of the electric compressor due to any cause. The voltage control unit is configured to control the application based on a high-pressure side pressure of the electric compressor.
A control device according to still another aspect of the present invention is used in an electric compressor in which a control device that controls a motor provided in the electric compressor is mounted integrally with a housing of the electric compressor. The control device includes a magnetism-resistant section formed in a sheet shape by sandwiching a conductive layer having an electric conductivity and a thermal conductivity, with insulating layers, and configured to cover a portion of a substrate of the control device. The magnetism-resistant section includes a portion at which the conductive layer is exposed, and is arranged such that the portion is in contact with any one of the housing and a part conducting heat to the housing.
The other objects, features, and advantages of the present invention are specifically set forth in or will become apparent from the following detailed description of the invention when read in conjunction with the accompanying drawings.